Schlafen, a new family of growth regulatory genes that affect thymocyte development

The Schlafen (Slfn) family of genes are differentially regulated during thy mocyte maturation and are preferentially expressed in the lymphoid tissues. Ectopic expression of the prototype member Slfn 1 early in the T lineage p rofoundly alters cell growth and development. In these mice, the DP thymocy tes fail to complete maturation, and, depending on the transgene dosage, th e number of thymocytes is reduced to 1%-30% of normal. Furthermore, express ion of the Schlafen family members in fibroblasts and thymoma cells either retards or ablates cell growth. The conceptual protein sequences deduced fo r each of the family members have no similarity to characterized proteins a nd must therefore participate in a heretofore unknown regulatory mechanism guiding both cell growth and T cell development.